XFS memory allocation deadlock in 2.6.38

['Christoph Hellwig']

On Wed, Mar 30, 2011 at 11:09:42AM +1100, Dave Chinner wrote:
> +	ext_buffer = kmem_alloc(XFS_IFORK_SIZE(ip, whichfork),
> +							KM_SLEEP | KM_NOFS);

The old code didn't use KM_NOFS, and I don't think it needed it either,
as we call the iop_format handlers inside the region covered by the
PF_FSTRANS flag.

Also I think the   routine needs to be under #ifndef XFS_NATIVE_HOST, as
we do not use it for big endian builds.